A conventional illuminator employed by an image reader apparatus or the like includes a lot of light sources arranged, such as LEDs, and transparent material guiding light emitted from the light sources. The illuminator lets the light from the light sources travel through the transparent material, and guides the light to a linear image reading area, whereby the surface of a document is uniformly illuminated(see, for example, Patent Document 1).
Moreover, in an illuminator according to another example, a transparent rod whose light outgoing face is a convex curved surface is used as a light guide, a light diffusion area is provided in the plane facing the curved surface, and LED devices as a light source are fixed on both ends of the transparent rod, to achieve a linear illuminator(see, for example, Patent Document 2).
Patent document 1: Japanese Patent Laid-Open No. 77975/2001
Patent document 2: Japanese Patent Laid-Open No. 232648/2002